Most people are called to marriage according to the Church. It is a 'natural vocation' which began in Genesis in order to fill up the kingdom of God with souls. It is a 'natural' call meaning instilled in the human being upon creation. Christ made it a sacrament and elevated Catholic marriage into something beyond just a 'natural' thing. And this is what separates a 'natural' marriage and a 'supernatural' marriage. The life of grace flows into the souls of two baptized person who marry whereas this is not the case for two non baptized souls. To dumb it down, the sacrament of marriage makes it drawn into the life of Christ. Non baptized souls participate in 'natural' marriages.
Religious callings are completely different. They are supernatural entirely. The Holy Spirit calls out to only a few souls and it is not 'natural' in any sense. Meaning, people are not born with this vocation but receive it from the Holy Spirit. Even if a person wanted they could not join any religious order, priesthood, etc. by sheer will without it ending in complete disaster.
The real question is not how do I know I'm called to marriage but how do I know if I'm called to a religious vocation?
From friends who've entered the religious world the same desires they've related to me: dissatifaction and uneasiness with world, an incompleteness and lack of peace in dating, an unsettled soul desiring something more, high idealism; Some have dated the best people and still felt that lack of peace in that God wanted more. I truly believe that if a person seeks out his will the Lord will give to a person a great serenity not as the world gives but a calming of the spirit which confirms the truth of a religious vocation.